It is known of in the art to make seats and frames separately, is preferably in different materials, to then assemble them to each other. The interconnection between the frame and the seat is usually made by riveting, bolting or by means of screws passing through the seat so as to engage in relative holes made in the frame.
Such structures have the drawback of requiring, for their assembly, the use of riveting machines or of staff specialised in assembly operations and interconnecting parts by means of the aforementioned coupling devices.
For this reason, the seat elements of the prior art are usually assembled during the production process so that the final product is for example a chair or stool already assembled and ready to use. The pre-assembled structure has the disadvantage however of proving cumbersome and inconvenient both to store and to transport.
Seat element structures are also known of in the art in two separate parts which can be attached to each other by shaped coupling means between respective counter-shaped portions of the frame and of the seat.
Such shaped coupling means do not however ensure stable and safe coupling over time. In other words with wear and on account of the inevitable production tolerances there is often annoying and unacceptable play between the seat and the frame.
In addition, the coupling means of the prior art tend to break during the assembly phase and often ruin the seat through abrasion during the assembly and/or subsequent dismantling phase.
The deterioration of the seat, even if on the under part of the seat and is therefore quite remote, is not acceptable in the case in which the seat is upholstered for example in a precious material. In addition, in the case of an upholstered seat, the abrasion and damage of the covering may lead the mechanism to jam.